Create custom action msg

#ros2   #python   #action   #custom messages  

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Table of Content

Actions are defined as .action file locate in action sub folder The best practice is to create a package dedicated to ROS2 custom messages. The package type is cmake_ament and naming the package with _interface suffix so it’ clear that the package is an interface package.

ros2 pkg create custom_interfaces
rm -rf include
rm -rf src
mkdir msg srv action

• Remove from the package the src and include folders
• Create folders for msg, srv, action sub folders/
• Add action file for example name it Counter.action
• Action files defined in this structure

# Request
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# Result
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# Feedback

Action Definition

action/Counter.action

int32 count
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int32 total
---
int32 current

CMakeLists

CMakeList.txt

cmake_minimum_required(VERSION 3.8)
project(action_tutorial_interfaces)

if(CMAKE_COMPILER_IS_GNUCXX OR CMAKE_CXX_COMPILER_ID MATCHES "Clang")
  add_compile_options(-Wall -Wextra -Wpedantic)
endif()

# find dependencies
find_package(ament_cmake REQUIRED)
find_package(rosidl_default_generators REQUIRED)

rosidl_generate_interfaces(${PROJECT_NAME}
  "action/MyAction.action"
)
ament_export_dependencies(rosidl_default_runtime)

ament_package()

CMakeLists

Keep each action,srv or msg in new line

Package.xml

Add to package.xml

  <buildtool_depend>rosidl_default_generators</buildtool_depend>
  <exec_depend>rosidl_default_runtime</exec_depend>
  <member_of_group>rosidl_interface_packages</member_of_group>

build and test

build

colcon build --packages-select action_tutorial_interfaces 

test

ros2 interface list | grep Counter

check

ros2 interface show custom_interfaces/action/Counter

#

int32 count
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int32 total
---
int32 current

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Resources

• Creating an action